HI
Just in case you can't bring her into the main cabin, don't drug her. I know it's quite common but my vet told me never to do it. What happens when you drug them is that the sedation lowers their heart rate, and they sleep. However, when their heart rate lowers, so does their core temperature and it can cause problems when they are already put into a freezing luggage cabin. The animal can get too cold, have medical complications or even freeze. (Don't laugh!

A dog acutally froze and EXPLODED two years ago on a North American flight from Europe. Eww.) You can give them something mild to calm them, but don't fully sedate them!